1. Field of the Invention
The present invention relates to an apparatus for sorting mixtures of minerals into constituent parts and then recombining the materials into mixtures containing two or more of the constituent parts in alterable predetermined ratios. More specifically, the apparatus of the present invention uses a plurality of density separators, control valves, sensors, and splitters, all operated under programmed control, to first divide a mixture of minerals into its constituent parts and then use the constituent parts to create one or more end products, each of a predetermined composition.
2. Description of the Prior Art
It is well known in the construction arts that the nature and durability of various construction materials which incorporates sand vary based upon the particle size distribution of the sand used. Thus, various techniques have been employed in the prior art to treat raw sand and other minerals, the constituent parts of which are of an unknown and non-uniform size, to obtain at least one sand product which meets the desired specification. These same techniques have been employed with other particulate materials.
The prior art techniques often incorporate the use of one or more density separators which divide a source material into a relatively coarse underflow fraction and a relatively fine overflow fraction. The density separators typically include equipment, such as a valve, for varying the size of the material as required by varying the flow rate of the under-flow fraction in relation to the pulp density from the density separator.
It is also useful, at times, to blend together two or more products of different particulate specifications in order to achieve a blended product which meets specifications demanded by a customer. One way of achieving such a blend would be to store in bins two or more different output fractions from the density separator and then draw from the bins whatever relative weights of materials are required for blending. This technique suffers from several disadvantages. First is the cost of the weigh scales and the bins. Second is the space required for such equipment. Third is the lack of uniformity of the blend produced with such equipment.
Another significant problem associated with blending operations relates to the efficiency of the process used. Efficiency, of course, is affected if sufficient quantities of each of the materials to be blended is not available. Thus, to maximize the yield of specified products from available raw material, there is a real need for a blending control strategy that is able to pace the flow rates of raw material, the constituent materials separated out from the raw material, and the end product or products. Likewise, it is desirable to establish ratios of different final products from a plant while at the same time maintaining the individual product integrity. This, realistically, can only be efficiently achieved by the automatic operation of the plant.